1. Field of the Invention
The invention is related to the field of perpendicular magnetic recording (PMR) on magnetic recording hard disk drive systems and, in particular, to fabricating a stitched wrap around shield for a PMR write head.
2. Statement of the Problem
Magnetic hard disk drive systems typically include a magnetic disk, a recording head having write and read elements, a suspension arm, and an actuator arm. As the magnetic disk is rotated, air adjacent to the disk surface moves with the disk. This allows the recording head (also referred to as a slider) to fly on an extremely thin cushion of air, generally referred to as an air bearing. When the recording head flies on the air bearing, the actuator arm swings the suspension arm to place the recording head over selected circular tracks on the rotating magnetic disk where signal fields are written to and read by the write and read elements, respectively. The write and read elements are connected to processing circuitry that operates according to a computer program to implement write and read functions.
In a disk drive utilizing perpendicular recording, data is recorded on a magnetic recording disk by magnetizing the recording medium in a direction perpendicular to the surface of the disk. In this type of recording, the magnetic easy axes of the magnetic grains which store the recorded data are arranged perpendicular to the disk surface, instead of parallel to the disk surface as is the case in longitudinal recording. Perpendicularly recorded data is more stable than longitudinal data, and the data can be recorded at a higher density than longitudinal data. The coercivity of the medium is higher, since the magnetic recording layer is in effect “inside the gap” between the head and a soft underlayer (SUL) that is located under the magnetic layer. In addition, for the same read head design, perpendicular data provides greater read back amplitude. The disk has a higher magnetic moment-thickness product (MrT). For the same physical width of the read head, the magnetic read width is narrower.
High track density heads use narrow write pole widths. A sufficiently short flare length (i.e., the distance between the ABS and the point where the write pole flares out) is used to maintain the write field strength of a narrow track width perpendicular write head. As a result, the widened portion of a write pole behind the flare point is close to the recording medium and can produce undesired fields to the extent that the data in adjacent tracks may be erased. A balance between writeability and adjacent track interference (ATI) is needed for high track density perpendicular write heads.
Wrap around shield designs are utilized for high track density recording to shield adjacent tracks from unintended recording. FIG. 1 illustrates an ABS view of a typical write head 100 with a wrap around shield 120. As shown in FIG. 1, wrap around shield 120 has a trailing shield 122 placed in the proximity of the trailing surface 112 of the write pole 110, separated from write pole 110 by a gap 135. The function of trailing shield 122 is to improve the write field gradient and transition curvature of write pole 110. Wrap around shield 120 also has side shields 124 and 126 disposed on sides of write pole 110. Side shields 124 and 126 are separated from write pole 110 by a gap 130. Utilizing wrap around shield 120, the fringe fields are mostly confined between write pole 110 and side shields 124 and 126 and therefore the fringe fields create much less interference with adjacent tracks. Gap 135 is smaller than gap 130, and the thickness for both is important for proper write performance, and thus, there is a need for accurately controlling the thickness of trailing gap 135 and side gap 130 during manufacturing.
In prior art processes, trailing shield 122 and side shields 124 and 126 are fabricated at the same time. As a result, the manufacturing process focuses more on the alignment of trailing shield 122 with write pole 110 than the alignment of side shields 124 and 126 with write pole 110. This is because the tolerance of aligning trailing shield 122 with write pole 110 is less than the tolerance of aligning side shields 124 and 126 with write pole 110. Further, prior art processes lack flexibility and require very aggressive design points, such as flare point and shield throat height, which are challenging for processing control during manufacture. Further, fabrication is more difficult because of the topography caused by present fabrication methods.